Tuberculosis Drug Interferes With HIV Treatment, JAMA Study Says

The antiretroviral drug nevirapine is less effective in people with HIV/tuberculosis coinfection who begin taking nevirapine at the same time as the TB treatment rifampicin, according to a study published in Wednesday's HIV/AIDS-themed issue of the Journal of the American Medical Association and released at theXVII International AIDS Conference in Mexico City,BBC News reports.

For the study, Andrew Boulle of the University of Cape Town in South Africa and colleagues analyzed outcomes from approximately 4,000 people who began antiretroviral therapy between 2001 and 2006 (BBC News, 8/4). The researchers assigned 2,035 people to begin HIV treatment with the antiretroviral efavirenz, 1,074 of whom had TB. The researchers assigned nevirapine to 1,935 people, 209 of whom also had TB. All of the study participants with TB received rifampicin.

Among people receiving nevirapine who also had TB, 16.3% were about twice as likely to have increased HIV viral loads after six months, compared with 8.3% among HIV-positive people taking nevirapine who did not have TB. In addition, patients with HIV/TB coinfection were more than twice as likely to develop treatment failure at a faster rate as those without TB. However, after 18 months, 80% of people with HIV/TB coinfection taking nevirapine had reduced HIV viral loads (AFP/Melbourne Herald Sun, 8/4). Nevirapine also was found to be effective among patients who started taking it before beginning TB treatment. The researchers found no difference in the effectiveness of efavirenz among people who took it alone and those who took it in combination with rifampicin (BBC News, 8/4).

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According to AFP/Herald Sun, the study's findings are important because approximately one-third of people living with HIV/AIDS also have TB, and the death rate among people with HIV/TB coinfection is five times greater than among those with only TB (AFP/Melbourne Herald Sun, 8/4). The findings also are important because physicians in developing countries often initiate antiretroviral therapy in TB clinics because TB is common among people living with HIV/AIDS, BBC News reports. In addition, nevirapine is commonly used as a first-line antiretroviral in developing countries because it is inexpensive and safe for pregnant women (BBC News, 8/4).

According to Boulle, it is unclear why rifampicin has an impact on nevirapine, but it is possible that the drugs have a shared toxicity when used in combination or that rifampicin induces a drug reaction when patients begin antiretroviral treatment (AFP/Melbourne Herald Sun, 8/4). Boulle said that further research on the interaction between nevirapine and rifampicin is needed given Africa's reliance on nevirapine-based therapies and the importance of treating TB in people with HIV/TB coinfection. Boulle added that a "striking" aspect of the study is that 40% of HIV-positive individuals starting antiretroviral treatment have concurrent TB, which "underscore[es] the public health importance of improving affordable treatment options" for patients with HIV/TB coinfection.

John Howson, associate director of the International HIV/AIDS Alliance, said that the study demonstrated that antiretroviral therapy may "compromise" TB treatment but added that "this needs more research" (BBC News, 8/4).

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